gildas-lormeau/SingleFile · error · Error

SingleFile capture config must be an object

Error message

SingleFile capture config must be an object

What it means

getCaptureConfig validates the optional 'config' field of an external capture message. null/undefined is allowed (defaults to {}), but any non-object value — including arrays — is rejected with 'SingleFile capture config must be an object'. This ensures capture options are a plain map of option names to values.

Source

Thrown at src/core/bg/external-messages.js:150

		return business.captureTab(currentTab, captureConfig);
	} else if (message && message.method) {
		const tabs = await browser.tabs.query({ currentWindow: true, active: true });
		const currentTab = tabs[0];
		if (currentTab) {
			return autosave.onMessageExternal(message, currentTab, sender);
		} else {
			return false;
		}
	}
}

function getCaptureConfig(message) {
	const { config } = message;
	if (config == null) {
		return {};
	}
	if (typeof config != "object" || Array.isArray(config)) {
		throw new Error("SingleFile capture config must be an object");
	}
	const captureConfig = {};
	CAPTURE_OPTION_NAMES.forEach(optionName => {
		if (config[optionName] !== undefined) {
			captureConfig[optionName] = config[optionName];
		}
	});
	return captureConfig;
}

async function queryTabs(options) {
	const tabs = await browser.tabs.query(options);
	return tabs.sort((tab1, tab2) => tab1.index - tab2.index);
}

View on GitHub (pinned to 517fb7c5cf)

Solutions

1. Pass config as a plain object keyed by capture option names, e.g. { backgroundSave: true }.
2. Parse JSON strings before sending: config = JSON.parse(configStr).
3. Convert arrays into an object map before sending.
4. Omit the config field entirely if you want defaults.

Example fix

// before
sendMessage({ method: 'capture', config: ['backgroundSave', 'removeHiddenElements'] });
// after
sendMessage({ method: 'capture', config: { backgroundSave: true, removeHiddenElements: true } });

function isValidCaptureConfig(config) {
  return config == null || (typeof config === 'object' && !Array.isArray(config));
}
if (!isValidCaptureConfig(myConfig)) throw new TypeError('config must be a plain object');

function isPlainObject(v) {
  return v !== null && typeof v === 'object' && !Array.isArray(v);
}

if (!isPlainObject(config) && config != null) {
  config = {}; // or normalize/parse before sending
}
await sendMessage({ method: 'capture', config });

When it happens

Trigger: Sending a capture message where message.config is a string, number, boolean, or an Array (arrays are explicitly rejected even though typeof Array === 'object').

Common situations: Callers JSON-stringify their config and forget to parse it; callers pass a list of option names instead of an options map; dynamic config built from query params stays a string.

Understand the failure class

Background: Schema validation failed / invalid input schema: payload rejected because its shape doesn't match the expected schema — this error's family across 28 libraries.

Related errors

• URL is empty
• Cannot identify the extension requesting SingleFile capture
• SingleFile capture was not approved for this extension
• First argument to Readability constructor should be a docume

AI-assisted analysis of gildas-lormeau/SingleFile@517fb7c5cf (2026-09-01). Data as JSON: /api/errors/b600a6a8b6e54d4f. Report an issue: GitHub.